Photosynthesis Experiments

Using Chromatography to Investigate Photosynthesis

Chromatography is a technique that can be used to identify which pigments are in the leaves of different plants. This allows us to identify what wavelengths of light a plant can absorb.

1) Extract the chlorophyll

Take some leaves from a plant that grows in the shade.
Place boiling water from a kettle into a beaker and dip a few leaves to kill them.
Tear up the leaves and grind with 5-10 cm³ of acetone in a pestle and mortar until you obtain a dark green chlorophyll extract. Add a pinch of sand to break up the cells.

2) Add the chlorophyll

Use a strip of chromatography paper, which fits into a boiling tube without touching the sides. Mark a line 1.5 cm from the bottom in pencil and in the centre put a cross.
Mark another line 2 cm from the top of the paper.
Pick up your chlorophyll solution using a capillary tube and place on the cross. Allow to dry.
Repeat 4-5 times to have a small, dense green spot.

3) Suspend the paper

Put 1.5 cm of acetone/petroleum solvent into the bottom of the boiling tube, using a funnel to avoid wetting the sides.
Suspend the paper using a drawing pin so that it just touches the solvent and leave.

4) Repeat the experiment

Repeat steps 1-3 using leaves from a plant that grows well in direct sunlight.
Remove the paper from each boiling tube when the solvent reaches the line at the top of the papers. Mark the positions of the pigments before they fade.

Illustrative background for 5) Calculate R<sub>f</sub>

Illustrative background for 5) Calculate R<sub>f</sub> ?? "content

5) Calculate R_f

Calculate the R_f values using:
- R_f = distance travelled by spot ÷ distance travelled by solvent
Find the pigment that corresponds with the given R_f value.

Investigating Dehydrogenase Activity in Chloroplasts

During the light-dependent reaction, NADP is reduced to NADPH. A dehydrogenase enzyme catalyses this reaction. This experiment will monitor dehydrogenase activity by using DCPIP, a redox indicator.

DCPIP

In this investigation, a blue dye (DCPIP) is used to monitor the rate of dehydrogenase activity. DCPIP is a redox indicator.
This means that it is blue in the oxidised state and colourless in its reduced state.
When electrons are released by the chlorophyll, DCPIP will change from blue to colourless.

1) Extracting chloroplasts

Put 50 cm³ of isolation medium into a beaker.
Tear eight spinach leaves into small pieces and put the pieces into the isolation medium in the beaker.
- Do NOT put pieces of the midrib or the leaf stalk into the beaker.
Half fill a large beaker with ice and place a small beaker on top of the ice.
When carrying out this step, all solutions and apparatus should be kept as cold as possible and the extraction should be carried out as quickly as possible.

2) Suspending chloroplasts

Put 3 layers of muslin over the top of the filter funnel and wet with the isolation medium. Rest the filter funnel in the small beaker on the ice.
Pour the spinach and isolation medium into the blender and blend for 15 seconds. Pour the blended mixture back into the beaker.
Pour your blended mixture through the muslin in the filter funnel. Carefully squeeze the muslin to assist the filtering process.
Label this filtrate which is in the small beaker on ice as ‘chloroplast suspension’.

3) Set up tubes A and B

Label five test tubes A, B, C, X and Y and stand them in the large beaker. Put the lamp about 10 cm away so that all tubes are illuminated. Set up tubes A and B as follows:
- Tube A - 5 cm³ DCPIP solution + 1 cm³ water + 1 cm³ chloroplast suspension. Immediately wrap the tube in aluminium foil to exclude light.
- Tube B - 5 cm³ DCPIP solution + 1 cm³ water + 1 cm³ isolation medium.
Tubes A and B are control experiments. Leave both tubes until the end of your investigation.

4) Set up tube C

Set up tube C as follows:
- Tube C - 6 cm³ water + 1 cm³ chloroplast suspension.
Tube C is for you to use as a standard to help you to determine when any colour change is complete.

5) Set up tube X

Set up tube X as follows:
- Tube X - 5 cm³ DCPIP solution + 1 cm³ water in the tube.
Add 1 cm³ chloroplast suspension to tube X, quickly mix the contents and start the timer.
Record in seconds how long it takes for the contents of tube X to change colour from blue-green to green. Use tube C to help you determine when the colour change is complete.
- Repeat this step four more times.

6) Set up tube Y

Set up tube Y as follows:
- Tube Y - 5 cm³ DCPIP solution + 1 cm³ ammonium hydroxide.
Add 1 cm³ chloroplast suspension to tube Y, quickly mix the contents and start the timer.
Record in seconds how long it takes for the contents of tube Y to change colour from blue-green to green. Use tube C to help you determine when the colour change is complete.
- Repeat this step four more times.

7) Record the results

Record your data in a suitable table.
At the end of your investigation, record the colour of the mixtures in tubes A and B.

1Cell Biology

2Molecular Biology

2.1Water

2.1.1Water & Hydrogen Bonding

2.1.2IB Multiple Choice - Water & Hydrogen Bonding

2.1.3Extended Response - Water

2.2Carbohydrates & Lipids

2.2.1Monosaccharides

2.2.2Disaccharides & Polysaccharides

2.2.3Triglycerides & Phospholipids

2.2.4Cellulose

2.2.5Starch & Glycogen

2.3Proteins

2.3.1Structure & Functions of Proteins

2.4Enzymes

2.4.1Enzymes

2.4.2Factors Affecting Enzyme Activity

2.4.3Enzyme-Controlled Reactions

2.4.4End of Topic Test - Enzymes

2.5Structure of DNA & RNA

2.5.1DNA & RNA

2.6DNA Replication, Transcription & Translation

2.6.1Protein Synthesis

2.6.2Transcription & Translation

2.6.3End of Topic Test - DNA, Genes & Protein Synthesis

2.6.4Exam-Style Question - Protein Synthesis

2.6.5End of Topic Test - Coronavirus Translation

2.6.6IB Multiple Choice - Transcription

2.6.7IB Multiple Choice - Translation

2.7Cell Respiration

2.7.1Overview of Respiration

2.7.2Anaerobic Respiration

2.7.3End of Topic Test - Anaerobic Respiration

2.7.4Respiration Experiments

2.7.5End of Topic Test - Respiration

2.7.6IB Multiple Choice - Respiration

2.8Photosynthesis

2.8.1Overview of Photosynthesis

3Genetics

4Ecology

4.1Species, Communities & Ecosytems

4.1.1Population Dynamics

4.1.2Communities & Measuring Diversity

4.1.3Relationships Between Populations

4.1.4Overview of Ecosystems

4.1.5Nutrient Cycles

4.1.6Fertilisers

4.1.7Eutrophication

4.1.8Chi-Squared Test

4.2Energy Flow

4.2.1Energy

4.2.2Energy Flow

4.2.3Biomass & Food Chains

4.2.4Heterotrophs & Autotrophs

4.3Carbon Cycle

4.3.1Carbon Cycle

4.4Climate Change

4.4.1Carbon Dioxide

4.4.2The Greenhouse Effect

4.4.3Global Warming

4.4.4Maintaining Biodiversity

5Evolution & Biodiversity

5.1Evidence for Evolution

5.1.1Evidence for Evolution - Fossils & DNA

5.1.2Evidence for Evolution - Anatomy & Geography

5.1.3IB Multiple Choice - Evidence for Evolution

5.1.4Extended Response - DNA & Evolution

5.2Natural Selection

5.2.1Introduction

5.2.2Evolutionary Fitness

5.2.3Natural Selection & Variation

5.2.4End of Topic Quiz - Natural Selection

5.2.5IB Multiple Choice - Natural Selection

5.2.6Speciation

5.3Classification of Biodiversity

5.3.1Introduction to Biodiversity

5.3.2Keystone Species

5.3.3Courtship & Ancestry

5.3.4Classification

5.4Cladistics

5.4.1Evolutionary Relationships

5.4.2IB Multiple Choice - Species & Taxonomy

6Human Physiology

6.1Digestion & Absorption

6.1.1Overview of Digestion

6.1.2Digestion in Mammals

6.1.3Absorption

6.1.4End of Topic Test - Substance Exchange & Digestion

6.1.5End of Topic Test - Substance Ex & Digestion

6.2The Blood System

6.2.1The Circulatory System

6.2.2The Heart

6.2.3Blood Vessels

6.2.4Cardiovascular Disease

6.3Defence Against Infectious Disease

6.3.1Immune System

6.3.2The Immune Response

6.3.3Antibodies

6.3.4Primary & Secondary Response

6.3.5Vaccines

6.3.6HIV

6.3.7End of Topic Test - Immune System

6.3.8Exam-Style Question - Immune System

6.3.9End of Topic Test - Immune System

6.4Gas Exchange

6.4.1Lung Structure & Alveoli

6.4.2Ventilation

6.4.3Lung Disease

6.4.4Lung Disease Data

6.5Neurons & Synapses

6.5.1Neuron Structure

6.5.2Transmission of an Impulse

6.5.3Speed of Transmission

6.5.4End of Topic Test - Neurones & Action Potentials

6.5.5Synapses

6.5.6Types of Synapse

6.5.7Medical Application

6.5.8End of Topic Test - Synapses

6.5.9End of Topic Test - Nervous Comm&Coord

6.6Hormones, HomeoStasis & Reproduction

6.6.1Overview of Homeostasis

6.6.2Blood Glucose Concentration

6.6.3Controlling Blood Glucose Concentration

6.6.4End of Topic Test - Blood Glucose

6.6.5Type I & Type II Diabetes

6.6.6Human Reproductive Systems

6.6.7Hormonal Control of the Menstrual Cycle

7AHL: Nucleic Acids

7.1DNA Structure & Replication

7.1.1DNA

7.1.2RNA

7.1.3DNA Replication

7.1.4DNA Replication - Summary

7.1.5IB Multiple Choice - DNA Replication

7.2Transcription & Gene Expression

7.2.1Introduction to Transcription & Protein Synthesis

7.2.2Types of RNA

7.2.3Transcription

7.2.4RNA Processing in Eukaryotes

7.2.5IB Multiple Choice - Transcription

7.3Translation

7.3.1Translation

7.3.2Retroviruses

7.3.3Scientific Practices: Coronavirus

7.3.4IB Multiple Choice - Translation

8AHL: Metabolism, Cell Respiration & Photosynthesis

8.1Metabolism

8.1.1Molecules to Metabolism

8.2Cell Respiration

8.2.1Glycolysis

8.2.2Aerobic Respiration

8.3Photosynthesis

8.3.1Light-Dependent Reaction

8.3.2Light-Independent Reaction

8.3.3End of Topic Test - Photosynthesis Reactions

8.3.4Limiting Factors

8.3.5Photosynthesis Experiments

8.3.6End of Topic Test - Photosynthesis

8.3.7End of Topic Test - Photosynthesis

9AHL: Plant Biology

9.1Transport in the Xylem of Plants

9.1.1Structure

9.1.2Cohesion-Tension Theory

9.1.3Investigating Transpiration Rate

9.2Transport in the Phloem of Plants

9.2.1Structure

9.2.2Translocation

9.3Growth in Plants

9.3.1Plant Tropisms

10AHL: Genetics & Evolution

10.1Meiosis

10.1.1Stages of Meiosis

10.2Inheritance

10.2.1Linked Genes

10.2.2Sex-Linked Genes

10.2.3Non-Nuclear Inheritance

10.2.4Chi-Squared Test

10.2.5End of Topic Quiz - Inheritance

10.2.6IB Multiple Choice - Non-Mendelian Genetics

10.2.7Introduction to Non-Mendelian Inheritance

10.2.8Extended Response - Inheritance

10.2.9Grade 4-5 (Scientific Practices) - Inheritance

10.3Gene Pools & Speciation

10.3.1Populations

10.3.2Mutations, Genetic Drift, & Gene Flow

10.3.3Speciation

10.3.4Rate of Speciation

10.3.5Allopatric & Sympatric Speciation

11AHL: Animal Physiology

11.1Antibody Production & Vaccination

11.1.1Immune System

11.1.2The Immune Response

11.1.3Antibodies

11.1.4Primary & Secondary Response

11.1.5Vaccines

11.2Movement

11.2.1Skeletal Muscle

11.2.2Sliding Filament Theory

11.2.3Contraction

11.3The Kidney & Osmoregulation

11.3.1Kidneys & Osmoregulation

Jump to other topics